2 * "splice": joining two ropes together by interweaving their strands.
4 * This is the "extended pipe" functionality, where a pipe is used as
5 * an arbitrary in-memory buffer. Think of a pipe as a small kernel
6 * buffer that you can use to transfer data from one end to the other.
8 * The traditional unix read/write is extended with a "splice()" operation
9 * that transfers data buffers to or from a pipe buffer.
11 * Named by Larry McVoy, original implementation from Linus, extended by
12 * Jens to support splicing to files, network, direct splicing, etc and
13 * fixing lots of bugs.
15 * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
16 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
17 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
21 #include <linux/file.h>
22 #include <linux/pagemap.h>
23 #include <linux/splice.h>
24 #include <linux/memcontrol.h>
25 #include <linux/mm_inline.h>
26 #include <linux/swap.h>
27 #include <linux/writeback.h>
28 #include <linux/export.h>
29 #include <linux/syscalls.h>
30 #include <linux/uio.h>
31 #include <linux/security.h>
32 #include <linux/gfp.h>
33 #include <linux/socket.h>
34 #include <linux/compat.h>
38 * Attempt to steal a page from a pipe buffer. This should perhaps go into
39 * a vm helper function, it's already simplified quite a bit by the
40 * addition of remove_mapping(). If success is returned, the caller may
41 * attempt to reuse this page for another destination.
43 static int page_cache_pipe_buf_steal(struct pipe_inode_info
*pipe
,
44 struct pipe_buffer
*buf
)
46 struct page
*page
= buf
->page
;
47 struct address_space
*mapping
;
51 mapping
= page_mapping(page
);
53 WARN_ON(!PageUptodate(page
));
56 * At least for ext2 with nobh option, we need to wait on
57 * writeback completing on this page, since we'll remove it
58 * from the pagecache. Otherwise truncate wont wait on the
59 * page, allowing the disk blocks to be reused by someone else
60 * before we actually wrote our data to them. fs corruption
63 wait_on_page_writeback(page
);
65 if (page_has_private(page
) &&
66 !try_to_release_page(page
, GFP_KERNEL
))
70 * If we succeeded in removing the mapping, set LRU flag
73 if (remove_mapping(mapping
, page
)) {
74 buf
->flags
|= PIPE_BUF_FLAG_LRU
;
80 * Raced with truncate or failed to remove page from current
81 * address space, unlock and return failure.
88 static void page_cache_pipe_buf_release(struct pipe_inode_info
*pipe
,
89 struct pipe_buffer
*buf
)
92 buf
->flags
&= ~PIPE_BUF_FLAG_LRU
;
96 * Check whether the contents of buf is OK to access. Since the content
97 * is a page cache page, IO may be in flight.
99 static int page_cache_pipe_buf_confirm(struct pipe_inode_info
*pipe
,
100 struct pipe_buffer
*buf
)
102 struct page
*page
= buf
->page
;
105 if (!PageUptodate(page
)) {
109 * Page got truncated/unhashed. This will cause a 0-byte
110 * splice, if this is the first page.
112 if (!page
->mapping
) {
118 * Uh oh, read-error from disk.
120 if (!PageUptodate(page
)) {
126 * Page is ok afterall, we are done.
137 const struct pipe_buf_operations page_cache_pipe_buf_ops
= {
139 .confirm
= page_cache_pipe_buf_confirm
,
140 .release
= page_cache_pipe_buf_release
,
141 .steal
= page_cache_pipe_buf_steal
,
142 .get
= generic_pipe_buf_get
,
145 static int user_page_pipe_buf_steal(struct pipe_inode_info
*pipe
,
146 struct pipe_buffer
*buf
)
148 if (!(buf
->flags
& PIPE_BUF_FLAG_GIFT
))
151 buf
->flags
|= PIPE_BUF_FLAG_LRU
;
152 return generic_pipe_buf_steal(pipe
, buf
);
155 static const struct pipe_buf_operations user_page_pipe_buf_ops
= {
157 .confirm
= generic_pipe_buf_confirm
,
158 .release
= page_cache_pipe_buf_release
,
159 .steal
= user_page_pipe_buf_steal
,
160 .get
= generic_pipe_buf_get
,
163 static void wakeup_pipe_readers(struct pipe_inode_info
*pipe
)
166 if (waitqueue_active(&pipe
->wait
))
167 wake_up_interruptible(&pipe
->wait
);
168 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
172 * splice_to_pipe - fill passed data into a pipe
173 * @pipe: pipe to fill
177 * @spd contains a map of pages and len/offset tuples, along with
178 * the struct pipe_buf_operations associated with these pages. This
179 * function will link that data to the pipe.
182 ssize_t
splice_to_pipe(struct pipe_inode_info
*pipe
,
183 struct splice_pipe_desc
*spd
)
185 unsigned int spd_pages
= spd
->nr_pages
;
186 int ret
= 0, page_nr
= 0;
191 if (unlikely(!pipe
->readers
)) {
192 send_sig(SIGPIPE
, current
, 0);
197 while (pipe
->nrbufs
< pipe
->buffers
) {
198 int newbuf
= (pipe
->curbuf
+ pipe
->nrbufs
) & (pipe
->buffers
- 1);
199 struct pipe_buffer
*buf
= pipe
->bufs
+ newbuf
;
201 buf
->page
= spd
->pages
[page_nr
];
202 buf
->offset
= spd
->partial
[page_nr
].offset
;
203 buf
->len
= spd
->partial
[page_nr
].len
;
204 buf
->private = spd
->partial
[page_nr
].private;
211 if (!--spd
->nr_pages
)
219 while (page_nr
< spd_pages
)
220 spd
->spd_release(spd
, page_nr
++);
224 EXPORT_SYMBOL_GPL(splice_to_pipe
);
226 ssize_t
add_to_pipe(struct pipe_inode_info
*pipe
, struct pipe_buffer
*buf
)
230 if (unlikely(!pipe
->readers
)) {
231 send_sig(SIGPIPE
, current
, 0);
233 } else if (pipe
->nrbufs
== pipe
->buffers
) {
236 int newbuf
= (pipe
->curbuf
+ pipe
->nrbufs
) & (pipe
->buffers
- 1);
237 pipe
->bufs
[newbuf
] = *buf
;
241 buf
->ops
->release(pipe
, buf
);
245 EXPORT_SYMBOL(add_to_pipe
);
247 void spd_release_page(struct splice_pipe_desc
*spd
, unsigned int i
)
249 put_page(spd
->pages
[i
]);
253 * Check if we need to grow the arrays holding pages and partial page
256 int splice_grow_spd(const struct pipe_inode_info
*pipe
, struct splice_pipe_desc
*spd
)
258 unsigned int buffers
= ACCESS_ONCE(pipe
->buffers
);
260 spd
->nr_pages_max
= buffers
;
261 if (buffers
<= PIPE_DEF_BUFFERS
)
264 spd
->pages
= kmalloc(buffers
* sizeof(struct page
*), GFP_KERNEL
);
265 spd
->partial
= kmalloc(buffers
* sizeof(struct partial_page
), GFP_KERNEL
);
267 if (spd
->pages
&& spd
->partial
)
275 void splice_shrink_spd(struct splice_pipe_desc
*spd
)
277 if (spd
->nr_pages_max
<= PIPE_DEF_BUFFERS
)
285 * generic_file_splice_read - splice data from file to a pipe
286 * @in: file to splice from
287 * @ppos: position in @in
288 * @pipe: pipe to splice to
289 * @len: number of bytes to splice
290 * @flags: splice modifier flags
293 * Will read pages from given file and fill them into a pipe. Can be
294 * used as long as it has more or less sane ->read_iter().
297 ssize_t
generic_file_splice_read(struct file
*in
, loff_t
*ppos
,
298 struct pipe_inode_info
*pipe
, size_t len
,
306 isize
= i_size_read(in
->f_mapping
->host
);
307 if (unlikely(*ppos
>= isize
))
310 iov_iter_pipe(&to
, ITER_PIPE
| READ
, pipe
, len
);
312 init_sync_kiocb(&kiocb
, in
);
313 kiocb
.ki_pos
= *ppos
;
314 ret
= in
->f_op
->read_iter(&kiocb
, &to
);
316 *ppos
= kiocb
.ki_pos
;
318 } else if (ret
< 0) {
319 if (WARN_ON(to
.idx
!= idx
|| to
.iov_offset
)) {
321 * a bogus ->read_iter() has copied something and still
322 * returned an error instead of a short read.
326 iov_iter_advance(&to
, 0); /* to free what was emitted */
329 * callers of ->splice_read() expect -EAGAIN on
330 * "can't put anything in there", rather than -EFAULT.
338 EXPORT_SYMBOL(generic_file_splice_read
);
340 const struct pipe_buf_operations default_pipe_buf_ops
= {
342 .confirm
= generic_pipe_buf_confirm
,
343 .release
= generic_pipe_buf_release
,
344 .steal
= generic_pipe_buf_steal
,
345 .get
= generic_pipe_buf_get
,
348 static int generic_pipe_buf_nosteal(struct pipe_inode_info
*pipe
,
349 struct pipe_buffer
*buf
)
354 /* Pipe buffer operations for a socket and similar. */
355 const struct pipe_buf_operations nosteal_pipe_buf_ops
= {
357 .confirm
= generic_pipe_buf_confirm
,
358 .release
= generic_pipe_buf_release
,
359 .steal
= generic_pipe_buf_nosteal
,
360 .get
= generic_pipe_buf_get
,
362 EXPORT_SYMBOL(nosteal_pipe_buf_ops
);
364 static ssize_t
kernel_readv(struct file
*file
, const struct iovec
*vec
,
365 unsigned long vlen
, loff_t offset
)
373 /* The cast to a user pointer is valid due to the set_fs() */
374 res
= vfs_readv(file
, (const struct iovec __user
*)vec
, vlen
, &pos
, 0);
380 ssize_t
kernel_write(struct file
*file
, const char *buf
, size_t count
,
388 /* The cast to a user pointer is valid due to the set_fs() */
389 res
= vfs_write(file
, (__force
const char __user
*)buf
, count
, &pos
);
394 EXPORT_SYMBOL(kernel_write
);
396 static ssize_t
default_file_splice_read(struct file
*in
, loff_t
*ppos
,
397 struct pipe_inode_info
*pipe
, size_t len
,
400 unsigned int nr_pages
;
401 unsigned int nr_freed
;
403 struct page
*pages
[PIPE_DEF_BUFFERS
];
404 struct partial_page partial
[PIPE_DEF_BUFFERS
];
405 struct iovec
*vec
, __vec
[PIPE_DEF_BUFFERS
];
410 struct splice_pipe_desc spd
= {
413 .nr_pages_max
= PIPE_DEF_BUFFERS
,
415 .ops
= &default_pipe_buf_ops
,
416 .spd_release
= spd_release_page
,
419 if (splice_grow_spd(pipe
, &spd
))
424 if (spd
.nr_pages_max
> PIPE_DEF_BUFFERS
) {
425 vec
= kmalloc(spd
.nr_pages_max
* sizeof(struct iovec
), GFP_KERNEL
);
430 offset
= *ppos
& ~PAGE_MASK
;
431 nr_pages
= (len
+ offset
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
433 for (i
= 0; i
< nr_pages
&& i
< spd
.nr_pages_max
&& len
; i
++) {
436 page
= alloc_page(GFP_USER
);
441 this_len
= min_t(size_t, len
, PAGE_SIZE
- offset
);
442 vec
[i
].iov_base
= (void __user
*) page_address(page
);
443 vec
[i
].iov_len
= this_len
;
450 res
= kernel_readv(in
, vec
, spd
.nr_pages
, *ppos
);
461 for (i
= 0; i
< spd
.nr_pages
; i
++) {
462 this_len
= min_t(size_t, vec
[i
].iov_len
, res
);
463 spd
.partial
[i
].offset
= 0;
464 spd
.partial
[i
].len
= this_len
;
466 __free_page(spd
.pages
[i
]);
472 spd
.nr_pages
-= nr_freed
;
474 res
= splice_to_pipe(pipe
, &spd
);
481 splice_shrink_spd(&spd
);
485 for (i
= 0; i
< spd
.nr_pages
; i
++)
486 __free_page(spd
.pages
[i
]);
493 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
494 * using sendpage(). Return the number of bytes sent.
496 static int pipe_to_sendpage(struct pipe_inode_info
*pipe
,
497 struct pipe_buffer
*buf
, struct splice_desc
*sd
)
499 struct file
*file
= sd
->u
.file
;
500 loff_t pos
= sd
->pos
;
503 if (!likely(file
->f_op
->sendpage
))
506 more
= (sd
->flags
& SPLICE_F_MORE
) ? MSG_MORE
: 0;
508 if (sd
->len
< sd
->total_len
&& pipe
->nrbufs
> 1)
509 more
|= MSG_SENDPAGE_NOTLAST
;
511 return file
->f_op
->sendpage(file
, buf
->page
, buf
->offset
,
512 sd
->len
, &pos
, more
);
515 static void wakeup_pipe_writers(struct pipe_inode_info
*pipe
)
518 if (waitqueue_active(&pipe
->wait
))
519 wake_up_interruptible(&pipe
->wait
);
520 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
524 * splice_from_pipe_feed - feed available data from a pipe to a file
525 * @pipe: pipe to splice from
526 * @sd: information to @actor
527 * @actor: handler that splices the data
530 * This function loops over the pipe and calls @actor to do the
531 * actual moving of a single struct pipe_buffer to the desired
532 * destination. It returns when there's no more buffers left in
533 * the pipe or if the requested number of bytes (@sd->total_len)
534 * have been copied. It returns a positive number (one) if the
535 * pipe needs to be filled with more data, zero if the required
536 * number of bytes have been copied and -errno on error.
538 * This, together with splice_from_pipe_{begin,end,next}, may be
539 * used to implement the functionality of __splice_from_pipe() when
540 * locking is required around copying the pipe buffers to the
543 static int splice_from_pipe_feed(struct pipe_inode_info
*pipe
, struct splice_desc
*sd
,
548 while (pipe
->nrbufs
) {
549 struct pipe_buffer
*buf
= pipe
->bufs
+ pipe
->curbuf
;
550 const struct pipe_buf_operations
*ops
= buf
->ops
;
553 if (sd
->len
> sd
->total_len
)
554 sd
->len
= sd
->total_len
;
556 ret
= buf
->ops
->confirm(pipe
, buf
);
563 ret
= actor(pipe
, buf
, sd
);
570 sd
->num_spliced
+= ret
;
573 sd
->total_len
-= ret
;
577 ops
->release(pipe
, buf
);
578 pipe
->curbuf
= (pipe
->curbuf
+ 1) & (pipe
->buffers
- 1);
581 sd
->need_wakeup
= true;
592 * splice_from_pipe_next - wait for some data to splice from
593 * @pipe: pipe to splice from
594 * @sd: information about the splice operation
597 * This function will wait for some data and return a positive
598 * value (one) if pipe buffers are available. It will return zero
599 * or -errno if no more data needs to be spliced.
601 static int splice_from_pipe_next(struct pipe_inode_info
*pipe
, struct splice_desc
*sd
)
604 * Check for signal early to make process killable when there are
605 * always buffers available
607 if (signal_pending(current
))
610 while (!pipe
->nrbufs
) {
614 if (!pipe
->waiting_writers
&& sd
->num_spliced
)
617 if (sd
->flags
& SPLICE_F_NONBLOCK
)
620 if (signal_pending(current
))
623 if (sd
->need_wakeup
) {
624 wakeup_pipe_writers(pipe
);
625 sd
->need_wakeup
= false;
635 * splice_from_pipe_begin - start splicing from pipe
636 * @sd: information about the splice operation
639 * This function should be called before a loop containing
640 * splice_from_pipe_next() and splice_from_pipe_feed() to
641 * initialize the necessary fields of @sd.
643 static void splice_from_pipe_begin(struct splice_desc
*sd
)
646 sd
->need_wakeup
= false;
650 * splice_from_pipe_end - finish splicing from pipe
651 * @pipe: pipe to splice from
652 * @sd: information about the splice operation
655 * This function will wake up pipe writers if necessary. It should
656 * be called after a loop containing splice_from_pipe_next() and
657 * splice_from_pipe_feed().
659 static void splice_from_pipe_end(struct pipe_inode_info
*pipe
, struct splice_desc
*sd
)
662 wakeup_pipe_writers(pipe
);
666 * __splice_from_pipe - splice data from a pipe to given actor
667 * @pipe: pipe to splice from
668 * @sd: information to @actor
669 * @actor: handler that splices the data
672 * This function does little more than loop over the pipe and call
673 * @actor to do the actual moving of a single struct pipe_buffer to
674 * the desired destination. See pipe_to_file, pipe_to_sendpage, or
678 ssize_t
__splice_from_pipe(struct pipe_inode_info
*pipe
, struct splice_desc
*sd
,
683 splice_from_pipe_begin(sd
);
686 ret
= splice_from_pipe_next(pipe
, sd
);
688 ret
= splice_from_pipe_feed(pipe
, sd
, actor
);
690 splice_from_pipe_end(pipe
, sd
);
692 return sd
->num_spliced
? sd
->num_spliced
: ret
;
694 EXPORT_SYMBOL(__splice_from_pipe
);
697 * splice_from_pipe - splice data from a pipe to a file
698 * @pipe: pipe to splice from
699 * @out: file to splice to
700 * @ppos: position in @out
701 * @len: how many bytes to splice
702 * @flags: splice modifier flags
703 * @actor: handler that splices the data
706 * See __splice_from_pipe. This function locks the pipe inode,
707 * otherwise it's identical to __splice_from_pipe().
710 ssize_t
splice_from_pipe(struct pipe_inode_info
*pipe
, struct file
*out
,
711 loff_t
*ppos
, size_t len
, unsigned int flags
,
715 struct splice_desc sd
= {
723 ret
= __splice_from_pipe(pipe
, &sd
, actor
);
730 * iter_file_splice_write - splice data from a pipe to a file
732 * @out: file to write to
733 * @ppos: position in @out
734 * @len: number of bytes to splice
735 * @flags: splice modifier flags
738 * Will either move or copy pages (determined by @flags options) from
739 * the given pipe inode to the given file.
740 * This one is ->write_iter-based.
744 iter_file_splice_write(struct pipe_inode_info
*pipe
, struct file
*out
,
745 loff_t
*ppos
, size_t len
, unsigned int flags
)
747 struct splice_desc sd
= {
753 int nbufs
= pipe
->buffers
;
754 struct bio_vec
*array
= kcalloc(nbufs
, sizeof(struct bio_vec
),
758 if (unlikely(!array
))
763 splice_from_pipe_begin(&sd
);
764 while (sd
.total_len
) {
765 struct iov_iter from
;
769 ret
= splice_from_pipe_next(pipe
, &sd
);
773 if (unlikely(nbufs
< pipe
->buffers
)) {
775 nbufs
= pipe
->buffers
;
776 array
= kcalloc(nbufs
, sizeof(struct bio_vec
),
784 /* build the vector */
786 for (n
= 0, idx
= pipe
->curbuf
; left
&& n
< pipe
->nrbufs
; n
++, idx
++) {
787 struct pipe_buffer
*buf
= pipe
->bufs
+ idx
;
788 size_t this_len
= buf
->len
;
793 if (idx
== pipe
->buffers
- 1)
796 ret
= buf
->ops
->confirm(pipe
, buf
);
803 array
[n
].bv_page
= buf
->page
;
804 array
[n
].bv_len
= this_len
;
805 array
[n
].bv_offset
= buf
->offset
;
809 iov_iter_bvec(&from
, ITER_BVEC
| WRITE
, array
, n
,
810 sd
.total_len
- left
);
811 ret
= vfs_iter_write(out
, &from
, &sd
.pos
);
815 sd
.num_spliced
+= ret
;
819 /* dismiss the fully eaten buffers, adjust the partial one */
821 struct pipe_buffer
*buf
= pipe
->bufs
+ pipe
->curbuf
;
822 if (ret
>= buf
->len
) {
823 const struct pipe_buf_operations
*ops
= buf
->ops
;
827 ops
->release(pipe
, buf
);
828 pipe
->curbuf
= (pipe
->curbuf
+ 1) & (pipe
->buffers
- 1);
831 sd
.need_wakeup
= true;
841 splice_from_pipe_end(pipe
, &sd
);
846 ret
= sd
.num_spliced
;
851 EXPORT_SYMBOL(iter_file_splice_write
);
853 static int write_pipe_buf(struct pipe_inode_info
*pipe
, struct pipe_buffer
*buf
,
854 struct splice_desc
*sd
)
858 loff_t tmp
= sd
->pos
;
860 data
= kmap(buf
->page
);
861 ret
= __kernel_write(sd
->u
.file
, data
+ buf
->offset
, sd
->len
, &tmp
);
867 static ssize_t
default_file_splice_write(struct pipe_inode_info
*pipe
,
868 struct file
*out
, loff_t
*ppos
,
869 size_t len
, unsigned int flags
)
873 ret
= splice_from_pipe(pipe
, out
, ppos
, len
, flags
, write_pipe_buf
);
881 * generic_splice_sendpage - splice data from a pipe to a socket
882 * @pipe: pipe to splice from
883 * @out: socket to write to
884 * @ppos: position in @out
885 * @len: number of bytes to splice
886 * @flags: splice modifier flags
889 * Will send @len bytes from the pipe to a network socket. No data copying
893 ssize_t
generic_splice_sendpage(struct pipe_inode_info
*pipe
, struct file
*out
,
894 loff_t
*ppos
, size_t len
, unsigned int flags
)
896 return splice_from_pipe(pipe
, out
, ppos
, len
, flags
, pipe_to_sendpage
);
899 EXPORT_SYMBOL(generic_splice_sendpage
);
902 * Attempt to initiate a splice from pipe to file.
904 static long do_splice_from(struct pipe_inode_info
*pipe
, struct file
*out
,
905 loff_t
*ppos
, size_t len
, unsigned int flags
)
907 ssize_t (*splice_write
)(struct pipe_inode_info
*, struct file
*,
908 loff_t
*, size_t, unsigned int);
910 if (out
->f_op
->splice_write
)
911 splice_write
= out
->f_op
->splice_write
;
913 splice_write
= default_file_splice_write
;
915 return splice_write(pipe
, out
, ppos
, len
, flags
);
919 * Attempt to initiate a splice from a file to a pipe.
921 static long do_splice_to(struct file
*in
, loff_t
*ppos
,
922 struct pipe_inode_info
*pipe
, size_t len
,
925 ssize_t (*splice_read
)(struct file
*, loff_t
*,
926 struct pipe_inode_info
*, size_t, unsigned int);
929 if (unlikely(!(in
->f_mode
& FMODE_READ
)))
932 ret
= rw_verify_area(READ
, in
, ppos
, len
);
933 if (unlikely(ret
< 0))
936 if (unlikely(len
> MAX_RW_COUNT
))
939 if (in
->f_op
->splice_read
)
940 splice_read
= in
->f_op
->splice_read
;
942 splice_read
= default_file_splice_read
;
944 return splice_read(in
, ppos
, pipe
, len
, flags
);
948 * splice_direct_to_actor - splices data directly between two non-pipes
949 * @in: file to splice from
950 * @sd: actor information on where to splice to
951 * @actor: handles the data splicing
954 * This is a special case helper to splice directly between two
955 * points, without requiring an explicit pipe. Internally an allocated
956 * pipe is cached in the process, and reused during the lifetime of
960 ssize_t
splice_direct_to_actor(struct file
*in
, struct splice_desc
*sd
,
961 splice_direct_actor
*actor
)
963 struct pipe_inode_info
*pipe
;
970 * We require the input being a regular file, as we don't want to
971 * randomly drop data for eg socket -> socket splicing. Use the
972 * piped splicing for that!
974 i_mode
= file_inode(in
)->i_mode
;
975 if (unlikely(!S_ISREG(i_mode
) && !S_ISBLK(i_mode
)))
979 * neither in nor out is a pipe, setup an internal pipe attached to
980 * 'out' and transfer the wanted data from 'in' to 'out' through that
982 pipe
= current
->splice_pipe
;
983 if (unlikely(!pipe
)) {
984 pipe
= alloc_pipe_info();
989 * We don't have an immediate reader, but we'll read the stuff
990 * out of the pipe right after the splice_to_pipe(). So set
991 * PIPE_READERS appropriately.
995 current
->splice_pipe
= pipe
;
1003 len
= sd
->total_len
;
1007 * Don't block on output, we have to drain the direct pipe.
1009 sd
->flags
&= ~SPLICE_F_NONBLOCK
;
1010 more
= sd
->flags
& SPLICE_F_MORE
;
1014 loff_t pos
= sd
->pos
, prev_pos
= pos
;
1016 ret
= do_splice_to(in
, &pos
, pipe
, len
, flags
);
1017 if (unlikely(ret
<= 0))
1021 sd
->total_len
= read_len
;
1024 * If more data is pending, set SPLICE_F_MORE
1025 * If this is the last data and SPLICE_F_MORE was not set
1026 * initially, clears it.
1029 sd
->flags
|= SPLICE_F_MORE
;
1031 sd
->flags
&= ~SPLICE_F_MORE
;
1033 * NOTE: nonblocking mode only applies to the input. We
1034 * must not do the output in nonblocking mode as then we
1035 * could get stuck data in the internal pipe:
1037 ret
= actor(pipe
, sd
);
1038 if (unlikely(ret
<= 0)) {
1047 if (ret
< read_len
) {
1048 sd
->pos
= prev_pos
+ ret
;
1054 pipe
->nrbufs
= pipe
->curbuf
= 0;
1060 * If we did an incomplete transfer we must release
1061 * the pipe buffers in question:
1063 for (i
= 0; i
< pipe
->buffers
; i
++) {
1064 struct pipe_buffer
*buf
= pipe
->bufs
+ i
;
1067 buf
->ops
->release(pipe
, buf
);
1077 EXPORT_SYMBOL(splice_direct_to_actor
);
1079 static int direct_splice_actor(struct pipe_inode_info
*pipe
,
1080 struct splice_desc
*sd
)
1082 struct file
*file
= sd
->u
.file
;
1084 return do_splice_from(pipe
, file
, sd
->opos
, sd
->total_len
,
1089 * do_splice_direct - splices data directly between two files
1090 * @in: file to splice from
1091 * @ppos: input file offset
1092 * @out: file to splice to
1093 * @opos: output file offset
1094 * @len: number of bytes to splice
1095 * @flags: splice modifier flags
1098 * For use by do_sendfile(). splice can easily emulate sendfile, but
1099 * doing it in the application would incur an extra system call
1100 * (splice in + splice out, as compared to just sendfile()). So this helper
1101 * can splice directly through a process-private pipe.
1104 long do_splice_direct(struct file
*in
, loff_t
*ppos
, struct file
*out
,
1105 loff_t
*opos
, size_t len
, unsigned int flags
)
1107 struct splice_desc sd
= {
1117 if (unlikely(!(out
->f_mode
& FMODE_WRITE
)))
1120 if (unlikely(out
->f_flags
& O_APPEND
))
1123 ret
= rw_verify_area(WRITE
, out
, opos
, len
);
1124 if (unlikely(ret
< 0))
1127 ret
= splice_direct_to_actor(in
, &sd
, direct_splice_actor
);
1133 EXPORT_SYMBOL(do_splice_direct
);
1135 static int wait_for_space(struct pipe_inode_info
*pipe
, unsigned flags
)
1137 while (pipe
->nrbufs
== pipe
->buffers
) {
1138 if (flags
& SPLICE_F_NONBLOCK
)
1140 if (signal_pending(current
))
1141 return -ERESTARTSYS
;
1142 pipe
->waiting_writers
++;
1144 pipe
->waiting_writers
--;
1149 static int splice_pipe_to_pipe(struct pipe_inode_info
*ipipe
,
1150 struct pipe_inode_info
*opipe
,
1151 size_t len
, unsigned int flags
);
1154 * Determine where to splice to/from.
1156 static long do_splice(struct file
*in
, loff_t __user
*off_in
,
1157 struct file
*out
, loff_t __user
*off_out
,
1158 size_t len
, unsigned int flags
)
1160 struct pipe_inode_info
*ipipe
;
1161 struct pipe_inode_info
*opipe
;
1165 ipipe
= get_pipe_info(in
);
1166 opipe
= get_pipe_info(out
);
1168 if (ipipe
&& opipe
) {
1169 if (off_in
|| off_out
)
1172 if (!(in
->f_mode
& FMODE_READ
))
1175 if (!(out
->f_mode
& FMODE_WRITE
))
1178 /* Splicing to self would be fun, but... */
1182 return splice_pipe_to_pipe(ipipe
, opipe
, len
, flags
);
1189 if (!(out
->f_mode
& FMODE_PWRITE
))
1191 if (copy_from_user(&offset
, off_out
, sizeof(loff_t
)))
1194 offset
= out
->f_pos
;
1197 if (unlikely(!(out
->f_mode
& FMODE_WRITE
)))
1200 if (unlikely(out
->f_flags
& O_APPEND
))
1203 ret
= rw_verify_area(WRITE
, out
, &offset
, len
);
1204 if (unlikely(ret
< 0))
1207 file_start_write(out
);
1208 ret
= do_splice_from(ipipe
, out
, &offset
, len
, flags
);
1209 file_end_write(out
);
1212 out
->f_pos
= offset
;
1213 else if (copy_to_user(off_out
, &offset
, sizeof(loff_t
)))
1223 if (!(in
->f_mode
& FMODE_PREAD
))
1225 if (copy_from_user(&offset
, off_in
, sizeof(loff_t
)))
1232 ret
= wait_for_space(opipe
, flags
);
1234 ret
= do_splice_to(in
, &offset
, opipe
, len
, flags
);
1237 wakeup_pipe_readers(opipe
);
1240 else if (copy_to_user(off_in
, &offset
, sizeof(loff_t
)))
1249 static int iter_to_pipe(struct iov_iter
*from
,
1250 struct pipe_inode_info
*pipe
,
1253 struct pipe_buffer buf
= {
1254 .ops
= &user_page_pipe_buf_ops
,
1259 bool failed
= false;
1261 while (iov_iter_count(from
) && !failed
) {
1262 struct page
*pages
[16];
1267 copied
= iov_iter_get_pages(from
, pages
, ~0UL, 16, &start
);
1273 for (n
= 0; copied
; n
++, start
= 0) {
1274 int size
= min_t(int, copied
, PAGE_SIZE
- start
);
1276 buf
.page
= pages
[n
];
1279 ret
= add_to_pipe(pipe
, &buf
);
1280 if (unlikely(ret
< 0)) {
1283 iov_iter_advance(from
, ret
);
1292 return total
? total
: ret
;
1295 static int pipe_to_user(struct pipe_inode_info
*pipe
, struct pipe_buffer
*buf
,
1296 struct splice_desc
*sd
)
1298 int n
= copy_page_to_iter(buf
->page
, buf
->offset
, sd
->len
, sd
->u
.data
);
1299 return n
== sd
->len
? n
: -EFAULT
;
1303 * For lack of a better implementation, implement vmsplice() to userspace
1304 * as a simple copy of the pipes pages to the user iov.
1306 static long vmsplice_to_user(struct file
*file
, const struct iovec __user
*uiov
,
1307 unsigned long nr_segs
, unsigned int flags
)
1309 struct pipe_inode_info
*pipe
;
1310 struct splice_desc sd
;
1312 struct iovec iovstack
[UIO_FASTIOV
];
1313 struct iovec
*iov
= iovstack
;
1314 struct iov_iter iter
;
1316 pipe
= get_pipe_info(file
);
1320 ret
= import_iovec(READ
, uiov
, nr_segs
,
1321 ARRAY_SIZE(iovstack
), &iov
, &iter
);
1325 sd
.total_len
= iov_iter_count(&iter
);
1333 ret
= __splice_from_pipe(pipe
, &sd
, pipe_to_user
);
1342 * vmsplice splices a user address range into a pipe. It can be thought of
1343 * as splice-from-memory, where the regular splice is splice-from-file (or
1344 * to file). In both cases the output is a pipe, naturally.
1346 static long vmsplice_to_pipe(struct file
*file
, const struct iovec __user
*uiov
,
1347 unsigned long nr_segs
, unsigned int flags
)
1349 struct pipe_inode_info
*pipe
;
1350 struct iovec iovstack
[UIO_FASTIOV
];
1351 struct iovec
*iov
= iovstack
;
1352 struct iov_iter from
;
1354 unsigned buf_flag
= 0;
1356 if (flags
& SPLICE_F_GIFT
)
1357 buf_flag
= PIPE_BUF_FLAG_GIFT
;
1359 pipe
= get_pipe_info(file
);
1363 ret
= import_iovec(WRITE
, uiov
, nr_segs
,
1364 ARRAY_SIZE(iovstack
), &iov
, &from
);
1369 ret
= wait_for_space(pipe
, flags
);
1371 ret
= iter_to_pipe(&from
, pipe
, buf_flag
);
1374 wakeup_pipe_readers(pipe
);
1380 * Note that vmsplice only really supports true splicing _from_ user memory
1381 * to a pipe, not the other way around. Splicing from user memory is a simple
1382 * operation that can be supported without any funky alignment restrictions
1383 * or nasty vm tricks. We simply map in the user memory and fill them into
1384 * a pipe. The reverse isn't quite as easy, though. There are two possible
1385 * solutions for that:
1387 * - memcpy() the data internally, at which point we might as well just
1388 * do a regular read() on the buffer anyway.
1389 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1390 * has restriction limitations on both ends of the pipe).
1392 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1395 SYSCALL_DEFINE4(vmsplice
, int, fd
, const struct iovec __user
*, iov
,
1396 unsigned long, nr_segs
, unsigned int, flags
)
1401 if (unlikely(nr_segs
> UIO_MAXIOV
))
1403 else if (unlikely(!nr_segs
))
1409 if (f
.file
->f_mode
& FMODE_WRITE
)
1410 error
= vmsplice_to_pipe(f
.file
, iov
, nr_segs
, flags
);
1411 else if (f
.file
->f_mode
& FMODE_READ
)
1412 error
= vmsplice_to_user(f
.file
, iov
, nr_segs
, flags
);
1420 #ifdef CONFIG_COMPAT
1421 COMPAT_SYSCALL_DEFINE4(vmsplice
, int, fd
, const struct compat_iovec __user
*, iov32
,
1422 unsigned int, nr_segs
, unsigned int, flags
)
1425 struct iovec __user
*iov
;
1426 if (nr_segs
> UIO_MAXIOV
)
1428 iov
= compat_alloc_user_space(nr_segs
* sizeof(struct iovec
));
1429 for (i
= 0; i
< nr_segs
; i
++) {
1430 struct compat_iovec v
;
1431 if (get_user(v
.iov_base
, &iov32
[i
].iov_base
) ||
1432 get_user(v
.iov_len
, &iov32
[i
].iov_len
) ||
1433 put_user(compat_ptr(v
.iov_base
), &iov
[i
].iov_base
) ||
1434 put_user(v
.iov_len
, &iov
[i
].iov_len
))
1437 return sys_vmsplice(fd
, iov
, nr_segs
, flags
);
1441 SYSCALL_DEFINE6(splice
, int, fd_in
, loff_t __user
*, off_in
,
1442 int, fd_out
, loff_t __user
*, off_out
,
1443 size_t, len
, unsigned int, flags
)
1454 if (in
.file
->f_mode
& FMODE_READ
) {
1455 out
= fdget(fd_out
);
1457 if (out
.file
->f_mode
& FMODE_WRITE
)
1458 error
= do_splice(in
.file
, off_in
,
1470 * Make sure there's data to read. Wait for input if we can, otherwise
1471 * return an appropriate error.
1473 static int ipipe_prep(struct pipe_inode_info
*pipe
, unsigned int flags
)
1478 * Check ->nrbufs without the inode lock first. This function
1479 * is speculative anyways, so missing one is ok.
1487 while (!pipe
->nrbufs
) {
1488 if (signal_pending(current
)) {
1494 if (!pipe
->waiting_writers
) {
1495 if (flags
& SPLICE_F_NONBLOCK
) {
1508 * Make sure there's writeable room. Wait for room if we can, otherwise
1509 * return an appropriate error.
1511 static int opipe_prep(struct pipe_inode_info
*pipe
, unsigned int flags
)
1516 * Check ->nrbufs without the inode lock first. This function
1517 * is speculative anyways, so missing one is ok.
1519 if (pipe
->nrbufs
< pipe
->buffers
)
1525 while (pipe
->nrbufs
>= pipe
->buffers
) {
1526 if (!pipe
->readers
) {
1527 send_sig(SIGPIPE
, current
, 0);
1531 if (flags
& SPLICE_F_NONBLOCK
) {
1535 if (signal_pending(current
)) {
1539 pipe
->waiting_writers
++;
1541 pipe
->waiting_writers
--;
1549 * Splice contents of ipipe to opipe.
1551 static int splice_pipe_to_pipe(struct pipe_inode_info
*ipipe
,
1552 struct pipe_inode_info
*opipe
,
1553 size_t len
, unsigned int flags
)
1555 struct pipe_buffer
*ibuf
, *obuf
;
1557 bool input_wakeup
= false;
1561 ret
= ipipe_prep(ipipe
, flags
);
1565 ret
= opipe_prep(opipe
, flags
);
1570 * Potential ABBA deadlock, work around it by ordering lock
1571 * grabbing by pipe info address. Otherwise two different processes
1572 * could deadlock (one doing tee from A -> B, the other from B -> A).
1574 pipe_double_lock(ipipe
, opipe
);
1577 if (!opipe
->readers
) {
1578 send_sig(SIGPIPE
, current
, 0);
1584 if (!ipipe
->nrbufs
&& !ipipe
->writers
)
1588 * Cannot make any progress, because either the input
1589 * pipe is empty or the output pipe is full.
1591 if (!ipipe
->nrbufs
|| opipe
->nrbufs
>= opipe
->buffers
) {
1592 /* Already processed some buffers, break */
1596 if (flags
& SPLICE_F_NONBLOCK
) {
1602 * We raced with another reader/writer and haven't
1603 * managed to process any buffers. A zero return
1604 * value means EOF, so retry instead.
1611 ibuf
= ipipe
->bufs
+ ipipe
->curbuf
;
1612 nbuf
= (opipe
->curbuf
+ opipe
->nrbufs
) & (opipe
->buffers
- 1);
1613 obuf
= opipe
->bufs
+ nbuf
;
1615 if (len
>= ibuf
->len
) {
1617 * Simply move the whole buffer from ipipe to opipe
1622 ipipe
->curbuf
= (ipipe
->curbuf
+ 1) & (ipipe
->buffers
- 1);
1624 input_wakeup
= true;
1627 * Get a reference to this pipe buffer,
1628 * so we can copy the contents over.
1630 ibuf
->ops
->get(ipipe
, ibuf
);
1634 * Don't inherit the gift flag, we need to
1635 * prevent multiple steals of this page.
1637 obuf
->flags
&= ~PIPE_BUF_FLAG_GIFT
;
1641 ibuf
->offset
+= obuf
->len
;
1642 ibuf
->len
-= obuf
->len
;
1652 * If we put data in the output pipe, wakeup any potential readers.
1655 wakeup_pipe_readers(opipe
);
1658 wakeup_pipe_writers(ipipe
);
1664 * Link contents of ipipe to opipe.
1666 static int link_pipe(struct pipe_inode_info
*ipipe
,
1667 struct pipe_inode_info
*opipe
,
1668 size_t len
, unsigned int flags
)
1670 struct pipe_buffer
*ibuf
, *obuf
;
1671 int ret
= 0, i
= 0, nbuf
;
1674 * Potential ABBA deadlock, work around it by ordering lock
1675 * grabbing by pipe info address. Otherwise two different processes
1676 * could deadlock (one doing tee from A -> B, the other from B -> A).
1678 pipe_double_lock(ipipe
, opipe
);
1681 if (!opipe
->readers
) {
1682 send_sig(SIGPIPE
, current
, 0);
1689 * If we have iterated all input buffers or ran out of
1690 * output room, break.
1692 if (i
>= ipipe
->nrbufs
|| opipe
->nrbufs
>= opipe
->buffers
)
1695 ibuf
= ipipe
->bufs
+ ((ipipe
->curbuf
+ i
) & (ipipe
->buffers
-1));
1696 nbuf
= (opipe
->curbuf
+ opipe
->nrbufs
) & (opipe
->buffers
- 1);
1699 * Get a reference to this pipe buffer,
1700 * so we can copy the contents over.
1702 ibuf
->ops
->get(ipipe
, ibuf
);
1704 obuf
= opipe
->bufs
+ nbuf
;
1708 * Don't inherit the gift flag, we need to
1709 * prevent multiple steals of this page.
1711 obuf
->flags
&= ~PIPE_BUF_FLAG_GIFT
;
1713 if (obuf
->len
> len
)
1723 * return EAGAIN if we have the potential of some data in the
1724 * future, otherwise just return 0
1726 if (!ret
&& ipipe
->waiting_writers
&& (flags
& SPLICE_F_NONBLOCK
))
1733 * If we put data in the output pipe, wakeup any potential readers.
1736 wakeup_pipe_readers(opipe
);
1742 * This is a tee(1) implementation that works on pipes. It doesn't copy
1743 * any data, it simply references the 'in' pages on the 'out' pipe.
1744 * The 'flags' used are the SPLICE_F_* variants, currently the only
1745 * applicable one is SPLICE_F_NONBLOCK.
1747 static long do_tee(struct file
*in
, struct file
*out
, size_t len
,
1750 struct pipe_inode_info
*ipipe
= get_pipe_info(in
);
1751 struct pipe_inode_info
*opipe
= get_pipe_info(out
);
1755 * Duplicate the contents of ipipe to opipe without actually
1758 if (ipipe
&& opipe
&& ipipe
!= opipe
) {
1760 * Keep going, unless we encounter an error. The ipipe/opipe
1761 * ordering doesn't really matter.
1763 ret
= ipipe_prep(ipipe
, flags
);
1765 ret
= opipe_prep(opipe
, flags
);
1767 ret
= link_pipe(ipipe
, opipe
, len
, flags
);
1774 SYSCALL_DEFINE4(tee
, int, fdin
, int, fdout
, size_t, len
, unsigned int, flags
)
1785 if (in
.file
->f_mode
& FMODE_READ
) {
1786 struct fd out
= fdget(fdout
);
1788 if (out
.file
->f_mode
& FMODE_WRITE
)
1789 error
= do_tee(in
.file
, out
.file
,